How To Convert a Classic Mustang From Four-Lug to Five-Lug Wheels and Disc Brakes

Bucking the V-8 trend in a classic Mustang, what if you happen to want an inline six? At Mustang Monthly, we like six-poppers for their underdog demeanor and buzzy persona. A six-in-a-row rocks with endless possibilities, and let’s face it, most folks have a V-8. Not everyone has a six, and that makes it more unique. For one thing, six-cylinder Mustangs need not suffer from sloppy handling or inadequate braking. They have good weight distribution because there’s less iron in front.

Let’s look at how to make a six-cylinder Mustang safer. Between handling and braking, let’s first look at the most important of the two elements—braking. Brake safety begins with V-8 spec components, such as ’67 to ’70 spindles, which are thicker and stronger than ’65 to ’66 six-cylinder spindles. Small six-cylinder spindles won’t stand up to the torture of a canyon pass or road-race course.

Another issue is four-lug wheels, which are limited in scope with little available from the aftermarket for a six-cylinder Mustang. Finally, if you want really effective disc brakes for your six-cylinder Mustang you’re going to need disc brakes you can count on. That means going to a five-lug system.

We recently visited with Mustangs & Fast Fords OC (MFFOC) while the company was doing a front-disc brake and five-lug conversion. One of their customers with a ’68 six-cylinder Mustang wanted more effective braking, and they opted for four-piston V-8 disc brakes from MFFOC along with the corresponding five-lug conversion. MFFOC carried out the disc-brake swap, along with a rear axle flange five-lug conversion. Here’s how you can get there, too.

01. MFFOC has its own in-house front disc brake kit for classic Mustangs, which is a four-piston affair like you would see from ’65 to ’67. This is a nice kit that includes a power booster and a dual master cylinder with pressure differential and proportioning valves for greater safety and more effective braking. Everything is here to get the job done.

02. Classic Mustang drum brakes are notorious for their ineffectiveness. Six-cylinder drum brakes add insult to injury because are doubly ineffective. We’re going to pull these worn out drum brakes, fit this Mustang with front discs, and do a five-lug conversion. This is a ’68 Mustang drum brake with the spindle that we need for a disc-brake swap.

04. Once these bolts are removed, the entire drum brake assembly is taken off. You don’t have to disassemble the brake, simply remove the brake assembly and discard it.

05. The fine-thread disc brake spindle bolts get a thread locker for safety and are torqued to 35 to 45 foot-pounds. The bolt heads should face toward the rotor.

06. The caliper bracket and dust shield are positioned and secured, as shown. Caliper brackets are positioned toward the front of the vehicle.

07. Spindles should be dressed with emery cloth to remove fine irregularities and score the surface for adequate bearing security.

08. Once installed, check the bearings for smooth fit and security. Excessive play is cause for spindle replacement.

NO!!! Greasing Axle Spindles

Among the many popular brake job myths, the first is you need to coat axle spindles with wheel bearing grease. Not true! We will get arguments on this one, but wheel bearings must be secure on your Mustang’s front spindles. The bearing races should not turn on the spindles. This means you want metal-to-metal contact and solid security when the castle nut is torqued.

Here’s a good example of what not to do during a brake job. Never apply wheel-bearing grease to spindles or inner bearing races. You want bearing security, which comes from solid bearing contact. Some people argue this point and cite corrosion concerns. If you have a healthy bearing cap and axle seal, corrosion should never be a concern.

09. Clean the brake rotor surfaces thoroughly with a high-evaporative solvent like brake cleaner or lacquer thinner prior to installation. Also, keep surfaces free of skin oil, which means handling them by their edges.

10. When you install brake rotors make sure bearings are secured first, then spin the rotor and check for smoothness of rotation. Tighten the spindle nut to 17 to 25ft-lbs while spinning the rotor to seat the bearings. Then, back off one-half turn and snug the castle nut to 10 to15in-lbs. Do not over-tighten.

NO!!! Securing a Castle Nut

There’s always confusion on how to safely secure a castle nut. This is a demonstration of how not to secure a castle nut, MFFOC advises. Although this cotter pin will stay, this is not the best method.

This is the proper way to secure a spindle’s castle nut. The short leg of the cotter pin goes straight through, uncut, with the long leg wrapped around the spindle’s end as shown. This way, there’s less chance of interference with the dust cap.

Dust-cap installation without damage is doable using a segment of exhaust pipe correctly sized for your Mustang’s dust caps. Any auto parts store will stock the size you need.

11. Four-piston brake calipers are installed next. Use a thread locker on bolt threads and torque to 45 to 50ft-lbs.

14. When you perform your disc brake and five-lug conversion, opt for new pre-formed brake lines from Classic Tube. Reusing old brake lines is courting trouble. Classic Tube makes it easy with all the lines pre-formed and ready to go.

15. The completed four-piston retro-style disc brake upgrade is ready for operation. This is a nice piece available from MFFOC for not much money. Slotted rotors vent heat and friction related gas off and minimize fade.

Five-Lug Conversion

Five-lug rotors automatically come with the front disc brake conversion. However, unless you’re planning a Ford 8- or 9-inch rear axle transplant, you’re going to need to modify your six-cylinder rear axle flanges to five-lug. What’s more, this is an easy conversion for nearly any reputable machine shop to do, or you can ship your axles to MFFOC to have them perform this easy modification process.

16. Axles are positioned in a four-lug jig, as shown, and set up for conversion. One of the four lug holes is used as a reference point for spot-on accuracy. Holes are sized for a tight interference fit.

17. The new holes are beveled for easy lug stud installation.

18. New lug studs are pressed into place using a hydraulic press.

19. Brake drums get the same treatment. The drum is set up, as shown, and drilled following the same procedure.

We wrap up this disc brake and five-lug conversion with power brakes and an easy-to-access proportioning valve. The power booster and dual master cylinder fit perfectly between the shock tower and firewall. Though this is a ’68 Mustang, you can apply all the same elements to a ’65 to ’66. You’ll wind up with a user-friendly classic Mustang with safer brakes and five-lug wheels for a greater choice of wheel and tire sizes.

22. We’re installing a new brake pressure differential valve and switch, which eliminates any brake hydraulic system concerns. It is suggested you replace all steel brake lines with pre-formed galvanized or stainless steel brake lines from Classic Tube. They arrive on your doorstep ready for installation. Opt for StopFlex hoses from Classic Tube while you’re replacing everything.

23. Here’s the power brake booster from MFFOC. We left the master cylinder out of this image to allow you to see the bracket and proportioning valve. It’s easy to access and adjust.